Preamp for 6N3 tube

[mprivitera1]

Why make it more difficult than nessesairy
Like this you can adjust the gain between 0 and ~20dB (1x...10x)
The Ne bulb is to prevent high voltage between cathode and grid at start-up.
Mona

Hello Sir,

excuse my ignorance, but they are not very practical with valves. You in your schematic you put the volume potentiometer output again, or I misunderstand? you say you put a "bulb It is to prevent high voltage between cathode and grid at start-up" but what is this NE-2 bulb? a light bulb ?? ... Thank you for your clarification.....

 

[Ketje]

It's not a volume potentiometer, but a means to adjust the amount of feedback and hence the gain.
The NE-2 is a little neon bulb, i like that to keep it all tubes.You can use a 1N4148 diode, cathode diode at cathode tube, if you will.
Mona

 

[mprivitera1]

It's not a volume potentiometer, but a means to adjust the amount of feedback and hence the gain.
The NE-2 is a little neon bulb, i like that to keep it all tubes.You can use a 1N4148 diode, cathode diode at cathode tube, if you will.
Mona

..1N4148 Is available is already in my house, and did not understand what kind of device used for adjustment of feedback ...... maybe this?CA9V 47K ACP - Potenziometro: montaggio | TME - Componenti elettronici

Thank you

 

[Ketje]

With the cathode current there is some disipation needed, better a bigger one.
http://www.tme.eu/it/details/ca14v-47k/potenziometri-tht-mono-giro/acp/ca14zv125-47k-a2020/
Mona

 

[mprivitera1]

With the cathode current there is some disipation needed, better a bigger one.
CA14ZV12,5-47K A2020 ACP - Potenziometro: montaggio | TME - Componenti elettronici
Mona

thanks for your advice ..... but you've tried these modifications in your electronics?

 

[Ketje]

With the cathode current there is some disipation needed, better a bigger one.
CA14ZV12,5-47K A2020 ACP - Potenziometro: montaggio | TME - Componenti elettronici
Mona

Excuse me, i mixed up two circuits, one with the pot.m on the cathode i am busy with.
Isn't the case here, you can easely use the small one.And, if you allready have the 100k one even better.
Mona

 

[jean-paul]

@ckwong99: do you need so much gain (at all) ? If you could live with a buffer there are many simple circuits with 6N3.

It does not make much sense to use a high gain circuit when one does not need any gain

 

[mprivitera1]

Excuse me, i mixed up two circuits, one with the pot.m on the cathode i am busy with.
Isn't the case here, you can easely use the small one.And, if you allready have the 100k one even better.
Mona

ok, if you can clarify with the schematic ........ thanks

 

[mprivitera1]

@ckwong99: do you need so much gain (at all) ? If you could live with a buffer there are many simple circuits with 6N3.

It does not make much sense to use a high gain circuit when one does not need any gain

..as I have said on page # 17 ..... eliminating the output volume pot, and put it in the hall, now the control is correct and not requiring regular reduction in gain, but the sound quality do not really like. My intention is groped to improve the sound quality ...... I already have seen this PCB ...

 

[Ketje]

ok, if you can clarify with the schematic ........ thanks

The schematic doesn't change, only the value of the trimpotm., use 100k and it can be the small one from TME.
I had an other circuit on my mind with the trimpot on the cathode, lower value + more dissipation.The risk when doing more then one thing at the same time
Mona

 

[Koifarm]

Ckwong99,

use this schematic. It has 1x amplification and can drive headphones.

Schematic is used by NAD and Shanling.

 

[ckwong99]

Hi Paul i just want it as the line voltage gain control.
I am using B1 buffer play with dac direct input so the V gain seems not enough.

 

[mprivitera1]

..for supply fair I opened my page here http://www.diyaudio.com/forums/tubes-valves/304141-preamp-hengpen-13-6n3-advice.html#post4997078

 

[jean-paul]

Hi Paul i just want it as the line voltage gain control.
I am using B1 buffer play with dac direct input so the V gain seems not enough.

Normally this extra stage would be superfluous as DACs have 2V outputs. Most power amps get enough input voltage from a B1 with a DAC connected to it. Normally a B1 has volume control as per design.

Maybe adding volume control to the B1 as per design solves matters in a more easy way costing less time and making things more versatile with possible other sources.

 

[Ketje]

Quote:
Originally Posted by ckwong99>
"Hi Paul i just want it as the line voltage gain control.
I am using B1 buffer play with dac direct input so the V gain seems not enough."

Normally this extra stage would be superfluous as DACs have 2V outputs. Most power amps get enough input voltage from a B1 with a DAC connected to it. Normally a B1 has volume control as per design.

Maybe adding volume control to the B1 as per design solves matters in a more easy way costing less time and making things more versatile with possible other sources.

With a little mod the B1 can give gain too.No need for an extra (tube)stage.
Like this you get a gain over 4x.
Mona

 

[jean-paul]

Great minds think alike

 

[ckwong99]

Ok i will try it ，thx

 

[Blue Jinn]

THREAD REVIVAL.


I bought one of these (the red 6N3 "buffer board") to mess around with as a guitar and/or mic preamp. I eliminated the output pot. It seems to make sense to me to replace R5 with a pot, say 5k or 10k to attenuate by the amount of NFB rather than a pot on the input, especially if I put a step-up transformer on the input. Thoughts?

As an aside in the one I bought I eliminated the output pot, and on one channel eliminated the feedback and stuck a 1M resistor on the input jack. One has a ton of gain, the other makes for a decent "toob" effect. With guitar the lower gain side still has plenty of gain to drive a line input on a mixing board. On a Strat knockoff, on the hi-gain side I have to dial back the volume control to avoid clipping so there is a lot of loss or hum depending on the adjustment of the tone control. Buffering the input with the AMZ Fet Buffer helps calm that.